TWI427603B - Display and driving apparatus and method thereof - Google Patents

Description

Display and its driving device and driving method

The present invention relates to a flat display display technology, and more particularly to a drive device and a drive method for preventing a display from being noticeable by a human eye, and a display using the same.

With the evolution of optoelectronics and semiconductor technology, the development of flat panel displays has been promoted. In many flat panel displays, liquid crystal displays have superior characteristics such as high space utilization efficiency, low power consumption, no radiation and low electromagnetic interference. Become the mainstream of the market. The liquid crystal display generally includes a liquid crystal display panel and a backlight module, and since the liquid crystal display panel itself does not have self-luminous characteristics, the liquid crystal display panel must be provided with a backlight module to provide a surface light source required for the liquid crystal display panel, such a liquid crystal display. The image can be displayed to the user for viewing.

In today's liquid crystal displays, in order to improve the contrast, the brightness of the backlight source emitted by the backlight module is adjusted to enhance the dark state (lowest grayscale value) displayed on the liquid crystal display and the bright state (highest grayscale value). The contrast between the pictures. In general, in order to improve the contrast of the liquid crystal display, a method of reducing the brightness of the dark state picture is taken. For example, when the brightness of the bright picture of the liquid crystal display is 500 cd/m ² and the brightness of the dark picture is 0.5 cd/m ² , the comparison at this time is 1000 (ie, 500 ÷ 0.5=1000), if The brightness of the dark state picture is reduced to 0.1 cd/m ² , and the comparison at this time is 5000 (ie, 500 ÷ 0.1 = 5000). At the same time, the transmittance of the liquid crystal is also increased correspondingly to compensate the brightness of the display before the display is dimmed to the backlight source. Among them, dimming the brightness of the backlight source can also solve the situation that the liquid crystal display generates light leakage when displaying the dark state picture, and achieves the effect of saving energy.

However, the backlight module may have flicker after dimming, and the darker the backlight module is, the more obvious the flickering phenomenon will be. When the liquid crystal display is displaying a low gray scale picture, the human eye is less likely to notice the flicker phenomenon. When the liquid crystal display displays a high gray scale picture, the flicker phenomenon is easily perceived by the human eye, so that the display effect of the liquid crystal display is greatly reduced. .

In view of this, the present invention provides a driving device and method for a display, which can effectively solve the flicker phenomenon generated when the display adjusts the dynamic contrast value.

The invention provides a driving method of a display, comprising the following steps: First, obtaining a reference grayscale value of a picture signal. Next, a luminance lower limit value corresponding to one of the reference grayscale values is obtained, and the luminance lower limit value is changed according to the reference grayscale value. Then, the brightness of the backlight source corresponding to the picture signal is adjusted according to a dynamic contrast value, wherein the brightness of the backlight source is greater than or equal to the brightness lower limit value.

In an embodiment of the invention, the step of obtaining the brightness lower limit value corresponding to the reference gray scale value comprises: obtaining a brightness lower limit value via a lookup table, wherein the lookup table has a correspondence between the brightness lower limit value and the reference gray level value relationship.

In an embodiment of the present invention, the driving method of the display further includes: first, obtaining a voltage multiplying upper limit value corresponding to the reference grayscale value, wherein the voltage multiplying upper limit value is changed according to the reference grayscale value. Then, the pixel voltage corresponding to the picture signal is adjusted according to the dynamic contrast value to adjust the pixel voltage corresponding to the picture signal, wherein the pixel voltage multiplying factor is less than or equal to the voltage multiplying upper limit value.

In an embodiment of the present invention, the step of obtaining the voltage multiplying upper limit value corresponding to the reference grayscale value further comprises: obtaining a voltage multiplication upper limit value via a lookup table, the lookup table having a voltage multiplication upper limit value and a reference gray The correspondence between the order values.

In an embodiment of the invention, the step of obtaining a reference grayscale value of the picture signal comprises: Search for the highest grayscale value of the display as the reference grayscale value.

In an embodiment of the invention, the step of obtaining the reference grayscale value of the picture signal comprises: calculating an average grayscale value of the display picture as the reference grayscale value.

In an embodiment of the invention, the driving method of the display is adapted to drive a liquid crystal display.

The invention provides a driving device for another display, comprising a driving unit, a backlight module driving unit and a controller. The driving unit is coupled to a display panel for driving the display panel. The backlight module driving unit is coupled to a backlight module for driving the backlight module to generate a backlight source. The controller is coupled to the driver and the backlight module driving unit, and the controller is configured to obtain a reference grayscale value of a picture signal, and obtain a corresponding brightness lower limit value according to the reference grayscale value, and the brightness lower limit value is followed by the reference The grayscale value changes. Wherein, when the controller adjusts the brightness of one of the backlight sources corresponding to the picture signal according to a dynamic contrast value, the brightness of the backlight source is greater than or equal to the brightness lower limit value.

In an embodiment of the invention, the controller further includes a lookup table for obtaining a brightness lower limit value, and the lookup table has a correspondence relationship between the brightness lower limit value and the reference gray level value.

In an embodiment of the present invention, the controller further obtains a voltage multiplication upper limit value according to the reference grayscale value, and the voltage multiplication upper limit value changes according to the reference grayscale value, and the controller adjusts the picture signal according to the dynamic contrast value. When the pixel voltage corresponding to one of the pixel voltages is adjusted to adjust the pixel voltage corresponding to the picture signal, the pixel voltage multiplying factor is less than or equal to the voltage multiplying upper limit value.

In an embodiment of the present invention, the controller further includes a lookup table for obtaining a voltage multiplying upper limit value, and the lookup table has a correspondence relationship between the voltage multiplying upper limit value and the reference grayscale value.

In an embodiment of the invention, the controller is a timing controller.

In an embodiment of the invention, the driving device is adapted to drive a liquid crystal display.

From another point of view, the present invention further provides a display comprising a display panel, a driving unit, a backlight module, a backlight module driving unit and a controller. The driving unit is coupled to the display panel for driving the display panel, and the backlight module driving unit is coupled to the backlight module for driving the backlight module to generate a backlight source. The controller is coupled to the driving unit and the backlight module driving unit, configured to obtain a reference grayscale value of a picture signal, and obtain a corresponding lower brightness limit value according to the reference grayscale value, where the brightness lower limit value is The reference gray scale value is changed, wherein when the controller adjusts the brightness of the backlight source corresponding to the picture signal according to a dynamic contrast value, the brightness of the backlight source is greater than or equal to the brightness lower limit value.

When the display adjusts the backlight, the display can find the corresponding brightness lower limit value from the lookup table according to the reference grayscale value of the picture signal, and set the backlight brightness according to the setting, or adjust the transmittance of the display. The corresponding gray scale upper limit value is found from the upper limit of the voltage multiplication according to the reference gray scale value of the picture signal, and the pixel voltage is adjusted accordingly. The above described features and advantages of the present invention will be more apparent from the following description.

The invention is mainly for effectively avoiding the flicker phenomenon that the display is perceived by the human eye when adjusting the dynamic contrast value by adjusting the backlight source, and the following content will be detailed for the technical features of the present invention and the desired effect. The description is provided to provide a description of the skilled person in the related art of the present invention.

FIG. 1 is a block diagram of a system shown in a display 100 according to an embodiment of the invention. Referring to FIG. 1 , the display 100 of the present embodiment is exemplified by a liquid crystal display (LCD), and includes a liquid crystal display panel (LCD panel) 101, a backlight module 103, and The controller 107, the driving unit 111, and the driving device 105 constituted by the backlight module driving unit 113. The controller 107 is, for example, a timing controller (T-con), and the backlight source in the backlight module 103 is, for example, a light source formed by a Cold Cathode Fluorescence Lamp (CCFL). The unit 111 includes a gate driver and a source driver (not shown).

The driving unit 111 is coupled to the liquid crystal display panel 101 and controlled by the controller 107 for inputting a picture signal to a pixel capacitor in the liquid crystal display panel 101. The backlight module driving unit 113 is coupled to the backlight module 103 and controlled by the controller 107 for driving the backlight module 103 according to the light source signal LS1 output by the controller 107. The backlight module driving unit 113 includes a pulse width modulation unit and a transformer (not shown). The backlight module driving unit 113 outputs a Pulse Width Modulation (PWM) signal LS2 according to the received light source signal LS1 to adjust the brightness of the backlight source. In general, the duty cycle or dimming cycle of the pulse width modulation signal LS2 corresponds to the brightness emitted by the backlight source in the backlight module 103. For example, the brightness of the backlight generated by the backlight module 103 when the effective period is 50% will be half of that when the effective period is 100%.

The pixel gray scale value in the liquid crystal display panel 101 is determined by the pixel voltage input by the driving unit 111 and the brightness of the backlight module 103. In general, the higher the pixel voltage, the higher the transmittance of the liquid crystal, and the higher the gray scale value. When the display 100 wishes to change its dynamic contrast, the contrast value is usually adjusted according to a dynamic contrast value by adjusting the pixel voltage multiplier to increase or decrease the pixel voltage, and adjusting the brightness of the backlight module 103. . For example, when a dynamic contrast of 10 times or more is obtained, the brightness of the backlight module 103 can be reduced to 1/10 of the original when the screen of the low gray level is displayed (ie, the effective period of the pulse width modulation signal LS2 is adjusted to The original 1/10) or when displaying a high grayscale picture, increase the pixel voltage to increase the contrast (that is, adjust the pixel voltage multiplier to increase the pixel voltage). Of course, the above two methods can be used simultaneously.

However, when the brightness of the backlight module 103 is too low, flicker may occur, and under a fixed backlight brightness, if the gray level displayed on the screen is too high (ie, the pixel voltage is too high) , there will also be flickering. Therefore, in the embodiment, when the controller 107 adjusts the brightness of the backlight source corresponding to the picture signal according to a dynamic contrast value, the brightness of the backlight source is greater than or equal to a brightness lower limit value, and the picture signal is adjusted. When the corresponding pixel voltage is used, the pixel voltage multiplying factor is less than or equal to a voltage multiplying upper limit value. In this way, it is ensured that flicker is not generated under different gray levels of the screen, whether the backlight brightness or the pixel voltage multiplier is adjusted.

The brightness lower limit value and the voltage multiplication upper limit value may be stored in the controller 107 or in the memory of the display 103 in a lookup table, and the embodiment is not limited. As for the value setting in the lookup table, it depends on the different display models and the needs of the user. Since the flicker phenomenon is a phenomenon perceived by the human eye, it is possible to obtain the gray scale (voltage magnification) of the picture acceptable to the human eye under different backlight brightness by means of experimental values and statistical analysis.

The experimental method of determining the lookup table mainly includes the following three steps. First, under different grayscale brightness, the human eye will feel the grayscale value of the screen flickering, and then the light luminance difference is measured by the light measuring device. Value and make a reference form. Then, the brightness of the backlight module 103 (ie, the effective period of the pulse width modulation signal LS2) is sequentially adjusted, and the gray scale value of the signal is changed, and the gray corresponding to the backlight brightness can be found by using the above reference table. Upper limit of the order. Finally, the grayscale upper limit value corresponding to the different backlight brightness (which can also be said to be the lower limit of the backlight brightness corresponding to different screen gray levels) is used as the optimal value of the backlight brightness and the pixel signal required for establishing the dynamic backlight technology.

The numerical value of the above look-up table can be graphically represented as shown in FIG. 2. FIG. 2 is a graph showing the effective period of the pulse width modulation signal LS2 and its reference grayscale value according to an embodiment of the present invention. In FIG. 2, curve 210 is a combination of different reference grayscale values and effective periods, each point representing display 100 displaying a combination of different reference grayscale values and effective periods, and the reference grayscale values in FIG. 2 are via the screen. The signal is calculated and can be used to represent the grayscale distribution state of a picture. In addition, the calculation method of the reference grayscale value is, for example, the grayscale average value of all pixels in the picture, the highest grayscale value in the picture, or the grayscale weighted average of different regions. In addition, the dynamic image technology can also be used to determine the reference grayscale value. This embodiment does not limit the manner in which the reference grayscale value is generated.

When adjusting the backlight brightness of the screen, if it is located in the upper area of the curve, there is no combination of the human eye perceiving the flicker phenomenon, and in the lower area of the curve, there is a combination of the human eye perceiving the flicker phenomenon. For example, when the display 100 operates at the operating point A in FIG. 2 (ie, displaying a grayscale value of 150 and an effective period of 60%), the display 100 does not exhibit human-appreciable flicker. When the display 100 is operated at the operating point B, that is, the brightness of the backlight source corresponding to the effective period of 45%, and the reference gray scale value is 150, the brightness of the backlight source is such that the human eye can not detect the flicker phenomenon. The lower limit of brightness.

In other words, if the display 100 dims the brightness of the backlight source from the operating point B, that is, lowers the effective period (for example, the display 100 is operated at the operating point C, and its effective period is 40%), the display 100 may appear to the human eye. Feel the flicker. Therefore, the effective period corresponding to the lower limit of the brightness of the display 100 can be set according to the lookup table to prevent the display 100 from being noticeable by the human eye.

That is to say, in the embodiment, when the controller 107 adjusts the backlight brightness according to the dynamic contrast value, a brightness lower limit value is determined according to the current picture reference gray scale value. In the process of adjusting the brightness of the backlight, the lower limit of the brightness of the backlight is limited to be maintained above the curve 210 to avoid the problem of flickering of the picture.

On the other hand, when the pixel voltage multiplier is adjusted, the reference grayscale value corresponding to the picture signal changes due to the adjustment of the pixel voltage. If the brightness of the backlight module is fixed, when the displayed reference grayscale value is too high, the problem of flickering of the screen will also occur. Therefore, when the pixel voltage corresponding to the picture signal is adjusted according to the dynamic contrast value to adjust the pixel voltage corresponding to the picture signal, the pixel voltage multiplier has an upper limit value, and the pixel voltage multiplier must be less than or equal to the pixel voltage. Voltage override upper limit.

Please refer to FIG. 3. FIG. 3 is a graph of pixel voltage multiplying factor and its reference grayscale value according to an embodiment of the present invention. 3 is a data according to a lookup table, wherein the reference grayscale value refers to the reference grayscale value corresponding to the original picture signal, and the curve 310 represents the pixel voltage magnification at different reference grayscale values. Upper limit. When the adjusted pixel voltage magnification is above the curve 310, a problem of flickering of the screen occurs. Therefore, in the embodiment, when the controller 107 adjusts the pixel voltage corresponding to the picture signal according to the dynamic contrast value to adjust the pixel voltage corresponding to the picture signal, the pixel voltage multiplier is limited to be below the curve 310. Avoid the problem of flickering the picture.

Further explained below, for example, when the display 100 is operated at the operation point D in FIG. 3 (that is, the display reference grayscale value is 150 and the pixel voltage magnification is 1), the display 100 does not exhibit human-appreciable flicker. When the display 100 operates at the operating point E, that is, in the case where the pixel voltage magnification is 1.3 and the grayscale value is 150, the pixel voltage magnification at this time is a voltage magnification that does not cause the human eye to perceive the flicker phenomenon. Limit. Once the display 100 increases the transmittance from the operating point E, that is, increases the pixel voltage multiplier (for example, operating the display 100 at the operating point F with a pixel voltage of 1.5), the display 100 may be perceived by the human eye. phenomenon. Therefore, the voltage multiplying upper limit value of the display 100 can be set according to the voltage multiplication upper limit lookup table to prevent the display 100 from being noticeable by the human eye.

It can be seen from the disclosure of the prior art that when the liquid crystal display adjusts the dynamic contrast value, if the brightness of the backlight source emitted by the backlight module 103 is too low, that is, when the operation is at a lower effective period, there is a flicker phenomenon. . If the light transmittance of the liquid crystal display panel 101 is too high, that is, the pixel voltage multiplying factor for adjusting the pixel voltage is too high, the blinking phenomenon is also perceived by the human eye. In other words, when the display 100 adjusts the dynamic contrast, if the brightness of the backlight source is too low or the light transmittance is too high, it will be easy to simultaneously display a flicker phenomenon that is perceptible to the human eye.

In view of this, in the embodiment, when the display 100 adjusts the dynamic contrast value, the controller 107 first obtains a reference grayscale value of a picture signal, and then obtains a luminance lower limit value corresponding to one of the reference grayscale values, and the lower limit of the brightness. The value is changed according to the reference gray scale value, and then the controller adjusts the brightness of one of the backlight sources corresponding to the picture signal according to a dynamic contrast value, wherein the brightness of the backlight source is greater than or equal to the brightness lower limit value.

More specifically, after obtaining the reference gray scale of the picture signal, the controller 107 automatically finds the effective period corresponding to the reference gray scale from the lookup table of the backlight brightness to adjust the brightness of the backlight source to the corresponding brightness. Or, the upper limit value of the voltage magnification corresponding to the reference gray scale is found in the lookup table of the upper limit of the voltage multiplication ratio, and the pixel voltage multiplying factor is set to adjust the pixel voltage of the picture signal, wherein the pixel voltage multiplying ratio is less than or equal to the voltage multiplying ratio. Limit. In this way, the display 100 can be prevented from displaying the flicker that can be perceived by the human eye, and the effect of adjusting the dynamic contrast value can be achieved.

Based on the disclosure of the above embodiments, a driving method for a display will be summarized below for those of ordinary skill in the art. 4 is a flow chart of a driving method of a display according to an embodiment of the invention.

Referring to FIG. 4, first, in step S410, a reference grayscale value of a picture signal is obtained. Then, in step S420, a luminance lower limit value corresponding to one of the reference grayscale values is obtained, and the luminance lower limit value is changed according to the reference grayscale value. Finally, in step S430, the brightness of one of the backlight sources corresponding to the picture signal is adjusted according to a dynamic contrast value, wherein the brightness of the backlight source is greater than or equal to the brightness lower limit value.

In addition, after the reference grayscale value is obtained, a voltage multiplying upper limit value corresponding to the reference grayscale value may be acquired, and the voltage multiplying upper limit value is changed according to the reference grayscale value. Then, according to the dynamic contrast value, one pixel voltage multiplication corresponding to the picture signal is adjusted to adjust the pixel voltage corresponding to the picture signal, wherein the pixel voltage multiplying factor is less than or equal to the voltage multiplying upper limit value.

The brightness lower limit value or the voltage power upper limit value may be obtained from the lookup table according to the reference gray scale value. After obtaining the brightness lower limit value or the voltage multiplication upper limit value, the brightness of the backlight source or the pixel voltage can be adjusted according to the brightness lower limit value or the voltage magnification upper limit value, so that the adjustment dynamics can be ensured. When comparing values, it is effective to avoid the appearance of flashing pictures. For the rest of the details of the driving method of the display according to the embodiment, please refer to the description of the above embodiments, and the details are not described herein.

In summary, when the display is adjusting the backlight, the corresponding brightness lower limit value can be found from the lookup table according to the reference gray scale value of the picture signal, and the backlight brightness can be set according to the brightness of the display, or the transmittance of the display can be adjusted. The corresponding gray scale upper limit value is found from the upper limit of the voltage multiplication according to the reference gray scale value of the picture signal, and the pixel voltage is adjusted accordingly. In this way, when the display adjusts the dynamic contrast value, the display can effectively prevent the display from being noticeable by the human eye.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

100. . . monitor

101. . . LCD panel

103. . . Backlight module

105. . . Drive unit

107. . . Controller

111. . . Drive unit

113. . . Backlight module drive unit

210, 310. . . curve

S410~S430. . . Steps of the flowchart of the driving method of the display according to an embodiment of the present invention

FIG. 1 is a block diagram of a system shown in a display 100 according to an embodiment of the invention.

2 is a graph showing an effective period of a pulse width modulation signal and a reference gray scale value thereof according to an embodiment of the present invention.

3 is a graph of pixel voltage multiplier and its reference grayscale value in accordance with an embodiment of the present invention.

4 is a flow chart of a driving method of a display according to an embodiment of the invention.

S410~S430. . . Steps of the flowchart of the driving method of the display according to an embodiment of the present invention

Claims (15)

A driving method for a display, comprising the steps of: obtaining a reference grayscale value of a picture signal; and obtaining a brightness lower limit value corresponding to the reference gray level value, the brightness lower limit value being changed according to the reference gray level value; Adjusting, according to a dynamic contrast value, a brightness of a backlight source corresponding to the picture signal, wherein a brightness of the backlight source is greater than or equal to the brightness lower limit value; and obtaining a voltage multiplication upper limit value corresponding to the reference gray level value, The voltage multiplying upper limit value is changed according to the reference gray scale value; and the pixel voltage corresponding to the picture signal is adjusted according to the dynamic contrast value to adjust a pixel voltage corresponding to the picture signal, wherein the pixel voltage ratio is Less than or equal to the upper limit of the voltage multiplier. The driving method of the display of claim 1, wherein the step of obtaining the brightness lower limit value corresponding to the reference gray scale value comprises: obtaining the brightness lower limit value via a lookup table, the lookup table having the The correspondence between the lower limit value of the brightness and the reference gray scale value. The driving method of the display of claim 1, wherein the step of obtaining the voltage multiplying upper limit value corresponding to the reference gray scale value further comprises: obtaining the voltage multiplying upper limit value via a lookup table, The lookup table has a correspondence relationship between the voltage multiplying upper limit value and the reference gray scale value. The driving method of the display of claim 1, wherein the step of obtaining the reference grayscale value of the picture signal comprises: searching for the highest grayscale value of the display picture as the reference grayscale value. The driving method of the display of claim 1, wherein the step of obtaining the reference grayscale value of the picture signal comprises: calculating an average grayscale value of the display picture as the reference grayscale value. The driving method of the display of claim 1, wherein the driving method of the display is adapted to drive a liquid crystal display. A driving device for a display, comprising: a driving unit coupled to a display panel for driving the display panel; a backlight module driving unit coupled to a backlight module for driving the backlight module to generate a backlight a light source; and a controller coupled to the driving unit and the backlight module driving unit, wherein the controller is configured to obtain a reference grayscale value of a picture signal, and obtain a corresponding brightness according to the reference grayscale value a limit value, the brightness lower limit value is changed according to the reference gray scale value, wherein when the controller adjusts the brightness of the backlight source corresponding to the picture signal according to a dynamic contrast value, the brightness of the backlight source is greater than or The controller is further configured to obtain a voltage multiplying upper limit value according to the reference grayscale value, where the voltage multiplying upper limit value is changed according to the reference grayscale value, when the controller is based on the dynamic contrast When the value of the pixel voltage corresponding to the picture signal is adjusted to adjust the pixel voltage corresponding to the picture signal, the pixel voltage multiplying factor is less than or equal to the voltage multiplying upper limit value. The driving device of the display of claim 7, wherein the controller further comprises a lookup table for obtaining the brightness lower limit value, the lookup table having the brightness lower limit value and the reference gray scale value Correspondence relationship. The driving device of the display device of claim 7, wherein the controller further comprises a lookup table for obtaining the voltage multiplying upper limit value, the lookup table having the voltage multiplying upper limit value and the reference gray scale The correspondence of values. The driving device of the display of claim 7, wherein the controller is a timing controller. The driving device of the display of claim 7, wherein the driving device is adapted to drive a liquid crystal display. A display device includes: a display panel; a driving unit coupled to the display panel for driving the display panel; a backlight module; a backlight module driving unit coupled to the backlight module for driving the backlight The module is configured to generate a backlight source; and a controller is coupled to the driving unit and the backlight module driving unit, wherein the controller is configured to obtain a reference grayscale value of a picture signal, and obtain the reference grayscale value according to the reference grayscale value Corresponding to one of the brightness lower limit values, the brightness lower limit value is changed according to the reference gray scale value, Wherein, when the controller adjusts the brightness of the backlight source corresponding to the picture signal according to a dynamic contrast value, the brightness of the backlight source is greater than or equal to the brightness lower limit value, wherein the controller is further based on the reference gray level The value obtains a voltage multiplication upper limit value, and the voltage multiplication upper limit value is changed according to the reference gray scale value, and the controller adjusts the pixel voltage ratio corresponding to the picture signal according to the dynamic contrast value to adjust the picture signal. When the pixel voltage is corresponding, the pixel voltage multiplying factor is less than or equal to the upper limit of the voltage multiplying factor. The display device of claim 12, wherein the controller further comprises a lookup table for obtaining the brightness lower limit value, the lookup table having a correspondence relationship between the brightness lower limit value and the reference gray level value. The display device of claim 12, wherein the controller further comprises a lookup table for obtaining the voltage multiplying upper limit value, the lookup table having a correspondence between the voltage multiplying upper limit value and the reference grayscale value relationship. The display of claim 12, wherein the controller is a timing controller.